To fill the garden, the German agronomist Friedrich Schmidt imported more than five hundred species of plants, many of them arriving by ship, along with peacocks, ducks, and turtles to give the grounds the feel of a living menagerie. Not everything thrived. The dry Mediterranean heat proved merciless to the more tender imports, and many simply withered. But what survived took deep root, and today the garden shelters thousands of trees and tens of thousands of shrubs winding along shaded paths. Walk them now and you move through a botanical experiment nearly two centuries old, a place where European ambition met Greek climate and reached an uneasy, beautiful truce.

The garden does not let you forget where you are. Scattered among the flowerbeds lie ancient ruins, most of them Roman: column drums of every order and size, the elegant flourish of Corinthian capitals, fragments of mosaic, and the remains of a Roman villa. There is even a large marble inscription concerning the emperor and ordered by a Roman legionary officer from the region of Epirus who had fought against Germanic tribes. Few city parks anywhere ask you to step around two thousand years of stone while looking for a bench. Here, antiquity is simply part of the scenery, half-buried beneath the shade like the foundations of the city itself.

The garden was the unlikely stage for one of the strangest turning points in Greek history. On October 2, 1920, King Alexander was walking the grounds when a pet monkey bit him. The wound turned septic, and three weeks later he was dead. His death brought back his deposed father, Constantine I, reshaped the government, and helped unravel Greece's military campaign in Asia Minor - a chain of events that ended in catastrophe and the great population exchange of 1923. Winston Churchill, never one to understate, later wrote that it was "perhaps no exaggeration to remark that a quarter of a million persons died of this monkey's bite."

In the 1920s the gates were thrown open and the Royal Garden became the National Garden, free to all from sunrise to sunset, though it kept its royal title officially until 1974. The change suited it. The American writer Henry Miller, wandering through in 1939, called it unlike any park he had ever known - "the quintessence of a park, the thing one feels sometimes in looking at a canvas or dreaming of a place one would like to be in and never finds." Around its edges stand busts of the men who shaped modern Greece: Ioannis Kapodistrias, the first governor, and the poet Dionysios Solomos, who wrote the national anthem.

Today the garden is woven into the daily life of Athens. It sits directly behind the Greek Parliament and flows south toward the grand Zappeion Hall and the marble horseshoe of the Panathenaic Stadium, home of the first modern Olympics in 1896. Inside are a duck pond, a small botanical museum, a children's library, a cafe, and a quiet that feels impossible given the traffic just beyond the railings. In 2004 the state handed the garden to the city of Athens on a ninety-year lease - a queen's private retreat, now belonging to everyone.